Every year a substantial percentage of the world's grain and hay supply for animal feeds is contaminated by toxins produced by invading molds. Decreased feed nutritive value and instances of animal poisoning are most often traced to growth of various species of Aspergillus, Fuserium, and Penicillium in stored grain or other feeds. Mycotoxins affect feed nutritive value, livestock performance, and animal health. Mycotoxin contaminated feeds are considerably less palatable to the animal, and the resulting decreased intake levels may exacerbate poor performance and/or toxicity problems.
Mycotoxin formation may occur when the causative fungi grow on crops in the field, at harvest, in storage, or during feed processing; essentially whenever favorable conditions for their formation prevail. Generalizations about geographical distribution of particular types of mycotoxins are difficult due to widespread distribution of the causative fungi. However, aflatoxins and fumonisin tend to prevail in warmer climates, while cooler regions with higher moisture are subject to ochratoxin, zearalenone, vomitoxin (deoxynivalenol, DON), T2 toxin, and others. Each mycotoxin has its own particular effect, and all can be devastating. Co-contamination by one or more types of mycotoxin occurs naturally, and exerts a greater negative impact on health and productivity of livestock than contamination by individual mycotoxins.
The physical effects of mycotoxins range from reduced feed intake and poor feed conversion to a general inability of an animal to thrive. Symptoms vary according to toxin. Vomitoxin, called the feed refusal factor, affects mainly pigs. Zearalenone affects the reproductive organs of pigs and dairy cattle. Fumonisin causes a nervous disorder in horses due to its impact in the brain. Ochratoxin causes kidney damage. Poultry and pigs are sensitive to ochratoxin, whereas dairy cattle can tolerate higher levels of ochratoxin because of its biotransformation into a nontoxic form by ruminal bacteria. Aflatoxins, the most common mycotoxin, cause increased susceptibility to disease. At the organ or cellular level mycotoxins differ in their effects with severe damage done to the liver and kidney by aflatoxins and on reproductive organs by zearalenone. Other indices of mycotoxicosis include mammary gland swelling and ovarian atrophy (zearalenone), oral lesions in chicks (T2 toxins), nervous system disorders and necrosis of the extremities (ergot alkaloids). Mycotoxins may also impact human health, as many are transferred into milk or meat following ingestion by the animal. For example, aflatoxins appear in milk as aflatoxin M1, a metabolite.
Acute symptoms of mycotoxicosis are often relatively easy to identify. However, chronic symptoms including slightly diminished performance and/or immunosuppression may result in greater economic losses. Traditional methods of dealing with mycotoxins include use of mold inhibitors to prevent mold growth in stored feeds. However, particularly in the livestock industries, economic circumstances force producers to find ways to use mycotoxin-contaminated feeds. Common methods have included dilution of contaminated feeds with feedstuffs known to be free of mycotoxins, physical separation to remove highly contaminated feeds, and ammoniation or heating to detoxify the feeds. These methods are labor-intensive and uneconomical, and may be ineffective against certain mycotoxins.
A more viable method of dealing with mycotoxin-contaminated feeds is to blend in substance capable of binding out the toxins, thus preventing absorption of the toxins into the animal's bloodstream. Few chemicals have proven successful enough to use commercially. Among these, use of mineral clays as binders has proven common. For example, U.S. Pat. No. 5,149,549 teaches the use of a montmorillonite clay, particularly a bentonite clay, admixed with animal feeds as a mycotoxin binder. U.S. Pat. No. 5,165,946 teaches the use of a montmorillonite clay in combination with a suitable sequestrant, particularly phosphate and polyphosphate salts, as a mycotoxin binder. U.S. Pat. No. 5,639,492 further refines the art, teaching the use of an acid-activated calcium bentonite clay admixed with animal feeds to reduce effects of mycotoxin contamination. However, clays as mycotoxin binders have significant limitations. Clays must be included in animal feeds at high levels to effect significant mycotoxin binding. Additionally, most clays have a limited binding efficacy range, binding only aflatoxins to any significant extent Further, in domestic livestock production situations, excreted clays may cause problems with clogging of manure handling equipment. Thus, a need exists for a mycotoxin-binding agent, effective against a wide range of mycotoxins, which can be admixed with animal feeds at lower inclusion rates than is currently possible with substances commonly used to bind mycotoxins in feeds.